Underreamer



Dec. 2, 1952 R. WADDINGTON UNDERREAMER Filed June 2, 1950 E12 g- 5- F1 E- l-vs-ron RICH A RD GY A TTORNE Patented Dec. 2, 1952 UNDERREAMER Richard Waddington, Port Arthur, Ontario, Canada, assignor to Boyles Bros. Drilling (Eastern) Ltd., Port Arthur, Ontario, Canada, a corporation Application June 2, 1950, Serial No. 165,788 In Canada February 2, 1950 1 Claim. 1

This invention relates to a tool for drilling holes for easing or stand-pipe, through overburden or soft rock formations, and in particular to that type of tool known as an under reamer.

Under reamers are tools which carry a drill bit, or cutting blades and are themselves attached to drill rods which supply the rotative power for drilling. The purpose of the under reamer is to obviate the necessity of raising the casing every time the drill-bit or cutting blades must be changed. The function of the under reamer therefore, on being lowered to the bottom of the casing, is to expand and cause a hole to be drilled, which is of sufiicient diameter for the casing to follow, and on the wearing out of the bit or blades, to contract so that the under reamer, and the attached cutting means may be raised through the casing. In order to effect this expansion and contraction, under reamers, have in the past been complex mechanisms with a large number of moving parts. The complexity and number of moving parts have made under reamers expensive to construct and susceptible to breakage and clogging.

This invention contemplates an under reamer constructed of two principal moving parts which performs the functions of expansion and contraction and drilling.

The reduction of the number of principal moving parts to two, and the consequent simplification of design reduces the likelihood of breakage or clogging and the expense of constructing the under reamer. Also since the number of parts is vastly reduced, and the space in the casing utilized by the tool is substantially the same, the individual parts are larger and therefore sturdier, further decreasing the likelihood of breakage.

The under reamer comprises two members,

vertically disposed from one another, one attached to the drill rod and the other attached to the drill bit, both of which are substantially cylindrical in shape and which make a sliding fit with the casing, below which, a hole is to be drilled. The two members are so connected that member is held from above by the drill rod while 2 the lower member is pulled downward by the force of gravity and the under reamer is in tension. When the drill bit is in contact with the bottom of the hole, the upper member is pushed downward by the drill rod while the lower member is pushed upward by the earth reaction at the bottom of the shaft and the reamer is in compression. Thus the two members each having the same external diameter are coaxial while passing through the casing and may be raised or lowered as desired, but on reaching the bottom of the casing the lower member projects below the lower extremity of the casing, and at the same time the drill bit contacts the bottom of the hole and the cylindrical members become heteroaxial and the lower member and the drill bit pro- ,iect laterally beyond the walls of the casing. With the drill bit in this eccentric position, rotation of the drill rods is carried through the now rigid connection between the upper and lower members, and causes the eccentric drill bit to rotate and drill a hole large enough for the casing to follow. When it is desired to raise the under reamer out of the casing, the drill rod is raised until the force on the under reamer is again tensile, and the two members are then therefore semi-flexibly connected, and on further raising the drill rod, the lower member slips back into the casing, and the whole under reamer may then be raised.

The two members are a body and a bit-holder, the body is cylindrical in shape and has a rectangular bore in its lower end and a means to attach a drill rod at its upper end, while the bit-holder is also cylindrical in shape and has a rectilinear tongue extending contiguously upwardly therefrom. Both body and bit-holder make a sliding fit with the casing and in the case of the body, it is essential that the fit be accurate. The tongue from the bit-holder projects into the bore of the body, a set screw seated in the body projects into the bore and into a recess in the tongue. When there is no upward pressure on the bitholder, that is when the under reamer is being raised or lowered through the casing, the bitholder hangs, suspended by the set screw bearing on the upper surface of the recess. When there is upward pressure on the bit-holder, due to the reaction of the bottom of the shaft on the bit holder, sloped surfaces on the tongue and in the bore co-operate to force the bit-holder to one side until it projects laterally beyond the outside wall of the casing, so that the drill bit, attached to the bit holder, will, on rotation of the drill rod. drill a hole large enough for the casing to follow.

In the drawings which illustrate embodiments of the invention:

Figure 1 is a vertical cross section showing the under reamer when passing through the casing.

Figure 2 is a vertical cross section showing the under reamer in position for drilling.

Figure 3 is a vertical cross section showing a view of the bit-holder at right angles to that shown in Figs. 1 and 2.

Figure 4 is a vertical cross section showing a view of the body at right angles to that shown in Figs. 1 and 2.

Figure 5 is a plan view of the bit holder.

Figure 6 is a plan view of the body.

The body I I is cylindrical and makes a sliding fit with the interior of a cylindrical casing H3. The body I I has in its upper end female threading l2 to receive drill rods l3, and in its lower end a rectangular bore is which terminates in a sloping bearing surface l5. The sloping surface 15 is from high end wall It to low end wall I! and surface i5 is perpendicular to side walls 18 and 1.9. Thefemale threading and the rectangular bore are connected by a water passage 29. The body I! has a flat bottom surface 2| which meets the walls !6, 1'8, and Id along right angled edges while the right angled-edge which would be-formed by the intersection of wall i l and surface 2! is cut-off parallel to surface 15 to form chamfered surface 22.

Thebit-holder-23 has a tongue 2d contiguously extending therefrom, and has female threading'zt in its lower face to receive a drill bit 26 while the .tongue 23 has a steppedbevel shape defined by end walls 21, 29 and 31, parallel bevelled surfacesi28 and 3B and side walls 32 and 33.

The smaller tongue cross section is joined to the larger bit-holder cross section by means of chamfered surface 34 which is parallel to bevelled surfaces 28, and 30, base segments 35 and 36, shoulder 42 and chamferedsurface ii.

'The bit-holder 23 makes a sliding fit with the casing Ill and when in use, the bit-holder is disposed below the body, with the tongue 24 projectinginto the bore l4. A set screw 31 projecting into the bore M through wall to ends in a rectangular recess 38 of the tongue. Therefore as long as there is no upward pressure on the bit 26 the bit holder hangs down from the body held by the set screw 31 which bears on the upper surface 139 of the recess 38. In this position, as shownin Figure 1 the under reamer is raised and lowered through the casing. When the under reamer has been lowered to a position such that the bit-holder projects below the casing, thebit comes into contact with the bottom of the shaft and the drill-rods press downward on the body while the earth presses upward on the bit-holder. The body'and bit-holder are thus compressed. As this occurs the chamferedsurface-Z'Z rides'up the bevelled surface 39 forcing the tongueover until it rests against end wall liiof the bore. The bore-continues to ride 'over the tongue until the chamferedsurface 22-bears oil-chamfered surface 34*while atthe same time bottom surface 2| bears on segments 35 and 36 and shoulder 42; halting the'telescopic motion of the-body and'bit-holder, andat the same time wedging the tongue firmly in position.

The connection between the bodyand the bit- 7 holder is now rigidand the bit holder now is ec- 4 centric with respect to the body, and projects laterally beyond the walls of the casing. If the drill rods are now rotated the bit will drill a hole large enough for the casing to follow. If it is desired to wash out the drillings a water passage d0 may be drilled through the bit-holder so that pulled upward, and is guided back into the casing by chamfered surface 4! and can then be raised to the surface.

While the bodyand bit-holder are described as cylindrical, it is obvious that any exterior shape which will conveniently rotate in the cylindrical casing and make a sliding fit during that rotation, may be used, for example a rectangular body mightbe used as long as the edges simultaneously touched the casing walls and keptthe body from radial movement in the casing.

I claim:

In drilling apparatus, a hollow cylindrical casing, an under-reamer comprising a body slidably engaging the interior of said casing and having means for securing the body to the lower end of a drill rod within the casing, a bit holder slidably engaging the interior of said casing and having means fOI'SGCLlI'lllg a bit to the lower portion of the bit-holder, said body portion having a-cylindrical bore open at-its lower end and having an inclined upper end wall, said bit holder having an upwardly extending portion with an inclined upper surface opposed'to said upper end wall, the inclined upper surface being adapted to slide along the upper end wall when the lower portion of the bit holder emerges from the casing and compressively engages the material being drilled bringing the body and bit holder into heteroaxial relationship, means being provided to prevent vertical rotation of the bit holder with respect to the body, said means for preventing vertical rotation of the bit holder with respect to the body portion comprising a shoulder portion of the bit holder slidably engaging a side wall of the bore of the body when a side of the upwardly extending portion of the bit holder slidably engages the oppositeside wall of the bore, the upper surface defining said shoulder portion being inclined in the same direction as the inclination of the upper surface of the upwardly projecting portion so that it will be deflected by the lower edge of the body to assist in positioning the bit holder in ,heteroaxial relationship, and means semi-flexibly connecting the-body and the bit holder in coaxial relationship when the under reamer is within the casing.

RICHARD VVADDINGTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 774,071 Grifiith Nov 1, 1904 1,260,533 Freeon Mar. 26, 1918 1,387,032 Wright Aug. 9, 1921 1,637,268 Miller July 26, 1927 

